A measuring device as used for measuring structures on substrates used for the manufacture of wafers (masks) has been disclosed in the paper entitled “Pattern Placement Metrology for Mask Making” by Dr. Carola Bläsing. The paper was held at the Semicon Education Program Convention in Geneva on Mar. 31, 1998. The description given there is the basis for a coordinate measuring machine as used in carrying out the method according to the present invention.
German Patent Application DE 198 17 714 discloses a method for measuring structures on a mask surface. The mask is placed in a coordinate measuring device on a measuring stage translatable in a plane vertical to the optical axis of the imaging measuring system in an interferometrically measurable fashion. In the method described here the mask is aligned relative to the coordinate system of a measuring device.
U.S. Pat. No. 5,459,577 discloses a method for determining the position of structures on the surface of a substrate. Herein, the device measures a first degree of bending, wherein the first degree of bending is produced by a particular configuration of support points of the substrate. Subsequently a second degree of bending is measured produced by a different configuration of support points. The form of the bending differs according to the position and location of the support points for the substrate. As it cannot be guaranteed that the substrate is always placed in the same position on the support points, this would mean that a corresponding measurement of the degree of bending or deformation would have to be carried out on the basis of the position of the support points for each newly inserted substrate. This is extremely time-consuming and thus reduces the throughput of substrates when the positions of structures on the substrate are measured.
The article by K.-D. Röth and K. Rinn published in “Mitteilungen für Wissenschaft und Technik” Vol. XI, No. 5, page 130 to 135, October 1997, describes mask metrology and its use in semiconductor manufacture. The nominal accuracy of a coordinate measuring machine is determined by the orientation in which a mask is placed on a substrate holder. If, for example, the mask is measured in four orientations (0°, 90°, 180° and 270°), slightly different measuring results will be obtained for each orientation. This demonstrates quite clearly that the insertion of the substrate in the substrate holder and their subsequent orientation to a coordinate system of the measuring stage and/or coordinate measuring machine has a critical effect on the degree of bending and ultimately on the accuracy of the measured values determined for the individual structures on the substrate.
U.S. Patent Application 2004/0036850 A1 discloses a support system for a wafer. The support system is used in an exposure system for substrates on a wafer. Herein a substrate, a wafer, is suctioned onto a plurality of support points on the support system by means of a vacuum. The air pressure can be varied between the support points to adjust the degree of bending of the substrate between the support points. This does not deal with the problems arising from the measurement of structures on a substrate with a coordinate measuring machine.
U.S. Patent Applications 2003/0016338 and 2003/0118925 are also concerned with exposure apparatus for masks on a wafer. The problems arising from measuring structures on a substrate with a coordinate measuring machine are not addressed here.
German Patent Application DE 198 58 428 A1 discloses a traversable X/Y coordinate measuring stage of a coordinate measuring machine. The substrate with the structures to be measured is supported on three support points. A correction of the measured values of the positions of the structures with respect to the position of the substrate relative to the coordinate system of the coordinate measuring machine is not disclosed.